In the interest of bandwidth economy, technologies have been developed to enable the transmission of compressed speech between media gateways in a network. Specifically, upon receipt of a speech signal from an end user, a media gateway encodes (or “compresses”) the speech and sends the compressed speech to a remote media gateway in the network in the form of a compressed speech packet. At the remote gateway, the compressed speech is decoded (or “decompressed”) into a speech signal and sent to an end user telephony device over a communication link, typically in a pulse coded modulation (PCM) format. The transmission of compressed speech between media gateways results in bandwidth economy.
In order to provide conferencing functionality, it is possible to introduce a device known as a “conference bridge” into the above scenario. However, a conventional conference bridge operates on decompressed speech signals, which leads to various disadvantages. Specifically, the introduction of a conventional conference bridge between media gateways requires an extra decompression stage at each input to the conference bridge followed by an extra stage of compression at each output of the conferencing bridge. This is known as “tandem” operation of speech codecs caused by the use of a conventional conference bridge. The “tandem” operation of speech codecs described above induces a loss of perceived signal quality, as well as an increase in required processing power.
Therefore, as an improvement, the concept of a “tandem-free” conference bridge has been introduced. As described in, for example, published U.S. patent application Ser. No. 09/986,498 to Rabipour et al., filed on Nov. 9, 2001, published on Aug. 8, 2002, hereby incorporated by reference herein, and the references cited therein, the tandem-free conference bridge makes forwarding decisions on the basis of “auxiliary information” received together with compressed speech for each media stream. Because of the presence of auxiliary information, the tandem-free bridge need not actually decode the compressed speech, hence resulting in an improvement in end-to-end speech quality.
The reader may also find it useful to consult other references that describe tandem-free bridge capabilities, including U.S. patent application Ser. No. 09/475,047 entitled “Apparatus and Method for Packet-Based Media Communications” filed on Dec. 30, 1999; U.S. patent application Ser. No. 09/750,015 entitled “Apparatus and Method for Packet-Based Media Communications.” filed on Dec. 29, 2000, published on Jul. 4, 2002; and U.S. patent application Ser. No. 09/664,450 entitled “Apparatus and Method for Packet-Based Media Communications” filed on Sep. 18, 2000. The contents of each of these references is incorporated by reference herein.
However, conventional media gateways do not possess the additional ability to provide the auxiliary information expected by the tandem-free conference bridge, nor the additional ability to process the auxiliary information received from the tandem-free conference bridge.
One solution would be to provision all new media gateways with suitable hardware and/or software for tandem-free bridge compatibility in order to cover the eventuality of the media gateway participating in a conference call through a tandem-free bridge. However, this solution does not take into consideration the large number of media gateways that have already been deployed without the ability to generate or process auxiliary information. For these media gateways, an upgrade would now be required to render them compatible with a tandem-free conference bridge. This solution is both costly and inefficient. Moreover, some outdated equipment may not even be amenable to upgrades.
Against this background, it is clear that there is a need in the industry for an improved solution to allow media gateways to participate in a conference with a conference bridge that operates on compressed speech in a tandem-free mode, such that conferencing services can be introduced gradually and without a wholesale upgrade of deployed gateways.